1. Field of the Invention
The present invention generally relates to a thermal head which has new driving method and a thermal head drive circuit, and particularly relates to a thermal head driving method and a thermal head drive circuit for driving thermal heads.
2. Description of the Related Art
Thermal head drive circuits include IC-mounted type and diode matrix type.
FIG. 1 is a block diagram showing a configuration of an IC-mounted drive circuit 10.
The IC-mounted drive circuit 10 comprises heater elements 11 and a driver IC 12. Each of the heater elements has an end to which a common potential is applied and the other end connected to the driver IC 12. The driver IC 12 comprises flip-flops, latch and driver elements equal in number. The driver IC 12 sequentially transfers serially-transferred data items in synchronization with clock, latches the data items into the flip-flops at the time of printing, and drives drivers with strobe signals according to the data items latched in the flip-flops so as to apply current to the heater elements 11. With this configuration, the driver IC 12 needs to have the same number of drivers as the number of driver elements.
FIG. 2 is a block diagram showing a configuration of a diode matrix type drive circuit 20.
The diode matrix type drive circuit 20 comprises heater elements 21, a driver IC 22, and diode drive group control ICs 24. The heater elements 21 are divided into groups of n heater elements 21 each. The n heater elements 21 in each group are connected through corresponding backflow prevention diodes 23 to the corresponding drive group control IC 24. The driver IC 22 can drive n heater elements 21 independently at the same time, and can drive the heater elements 21 by group.
As described above, since IC-mounted drive circuits require the same number of drivers as the number of driver elements, the size of driver ICs is large. On the other hand, diode matrix type thermal head drive circuits require the same number of diodes as the number of driver elements, and therefore the size of the drive circuits is large.